Persistent Hole Burning Induced by Resonant Energy Migration

Abstract

Excitation energy migration is an important phenomenon at high concentration of luminescent chromophores. In the three-dimensional network [Ru(bpy)₃][NaCr(ox)₃] it is possible to unambiguously identify three different mechanisms for energy migration within the R₁ line of the ⁴A₂ →²E transition of Cr³+ [1]. In addition to the common temperature dependant phonon-assisted process, a resonant process between the zero field split components of the ⁴A₂ ground state leading to a multi-line pattern in a Fluorescence Line Narrowing spectrum and a quasi-resonant process within the same component leading to fast spectral diffusion can be identified at very low temperature.On the other hand, in On the other hand, in NaMgAl_1-xCr_x(ox)₃9H₂O/D₂O,X=0.1%it is possible to efficiently burn persistent spectral holes within the ⁴A₂ →²E absorption bands of Cr³⁺ based on a 1novel hole burning mechanism involving flips of non-coordinated water molecules [2]. Here, we showed that in an optimized sample of the latter compound with x = 0.3, it is possible to observe both phenomena, that is, resonant excitation energy migration and persistent spectral hole burning (see Fig. 1). In addition to the usual resonant hole and side holes spaced by the ground-state zero-field splitting, persistent spectral holes are also burnt by resonant energy migration.